The present invention relates to seals and more particularly to seals for reciprocating pistons which provides increased power output of the unit, for example, an internal combustion engine.
The rapid piston reciprocation in internal combustion engines often causes the typical compression ring to move radially out of sealing contact with the cylinder bore causing a loss of seal around the piston. Compressed gas then escapes around the ring resulting in a loss of power. This condition is well recognized in the art as "blow-by." Blow-by also occurs through the gap in the typical ring.
The prior art offers numerous solutions to the blow-by problem. One general solution is the so called L-shaped compression ring. Such rings are taught by U.S. Pat. Nos. 2,844,422 and 2,844,424. The L-shaped rings of these patents provides a relatively large radially extending base ring portion seated in ring grooves in the piston head and a longer axially extending ring portion which is moved into sealing engagement with the cylinder bore by compressed gas in the cylinder.
These rings have several disadvantages, most notable of which are that the relatively thick base portions will not provide the necessary flexibility of the axially extending flange to maintain good sealing contact with the cylinder bore. Power loss is also experienced in blow-by through the gap in the rings. Ring wear increases the size of the gap which increases the amount of blow-by. The Blow-by through the gap of the typical ring is necessary to drive the oil toward the pan and thereby preventing oil from accumulating or reservoiring below the ring.
The overall weight necessary for long life of these prior art designs subjects them to bouncing off the cylinder wall at high revolution per minute, i.e., above 3,000 causing loss of seal. Also the designs require more complex manufacturing with increased costs of the rings.
Applicant is further aware of an L-shaped piston ring that is manufcatured by Seal Power Corporation having a place of business at Muskegon, Mich., and marketed under the trademark "Head Land Ring." This ring has a radially extending base that seats in a ring groove and a slightly thinner flange which extends axially at approximately 90.degree. to the base. The flange thickness of one such ring is 0.050 inches and the base thickness is 0.063 inches and weighs approximately 17 grams. This ring suffers from the same disadvantages of the above cited patents, and in addition, the right angle flange orientation presents less area against which the gas under pressure can act to drive the flange into contact with the cylinder wall and the entire face of the flange contacts the cylinder wall requiring that it be machined.
Applicant's seal overcomes these disadvantages of the prior art by providing a two ring seal which seats in a common ring groove in the piston head. The two ring seal permits the upper ring to be very thin and, hence, very flexible for ease of flexing into good sealing relationship with the cylinder wall. This flexing is enhanced by the flange extending at an obtuse angle to the ring body portion thereby presenting greater area for the gas pressure to work against.
The reduced thickness of Applicant's upper ring provides less mass and less tendency to bounce off the cylinder wall and breaking the seal.
The other ring functions as a typical compression seal while supporting the thinner upper ring. The two rings are oriented with their gaps diametrically opposed to prevent blow-by through the aligned gap. As a result, a controlled "blow-by" is provided through an opening in one ring which communicates with a gap in the lower ring to prevent oil reservoiring beneath the rings.
The seal according to the present invention provides a very effective dual ring seal that minimizes oil reservoiring beneath the very effective seal, is relative inexpensive to manufacture due to the simplified design approach embodied therein.
These and other objects will become apparent in the detailed description of the preferred embodiment of the piston seal according to the present invention.